Many applications frequently request to access the same data multiple times. To improve the performance of these applications, developers have come up with many different optimizations. One of these optimizations is to store the most recently and/or frequently used items in a cache. Generally, a cache is a temporary storage area that is used to speed up repeated access by the application to the same data. Caches are typically created in a memory that may be more quickly accessed then where the data is permanently stored. For instance, a cache may be created in RAM instead of on a hard drive which takes longer to access. As a cache is limited in size, data is not stored in the cache permanently. Once the data is removed from the cache, access to the data is slower.
One example of a cache is a web browser's cache. The browser cache stores content associated with a user's recently accessed web pages on their hard drive. This helps to speed up requests for the same web pages since this web page data does not need to be retrieved again providing the web page has not changed since the last access. Similarly, many web servers include caches for frequently accessed items. For example, a web server may cache the most recent and/or frequently accessed content such that the server does not need to retrieve the content from another location each time the content is requested.